This invention relates to the catalytic alkylation of an isoparaffin with one or more olefins. It further relates to apparatus for carrying out alkylation.
The catalytic alkylation of an isoparaffin with one or more olefins to produce a branched chain paraffin is a commercially important process for producing high-octane gasoline. Conventional catalytic alkylation processes generally involve the reaction of an isoparaffin such as isobutane with an olefin such as propylene and/or a butylene in the presence of a liquid alkylation catalyst, followed by the separation of the unreacted and product hydrocarbons from the catalyst in a settling zone and purification of the product alkylate. Because of the exothermic nature of the reaction, it is necessary to provide means of controlling the temperature inside the reaction vessel and maintaining the optimum alkylation temperature. Methods of maintaining this temperature include recycling the catalyst from the settling zone through a cooler and back to the reaction zone and recycling hydrocarbons from the settling zone through a cooler to be added to the hydrocarbon feed stream. Because of the corrosiveness of the catalysts used in alkylation, it is desirable to minimize catalyst circulation. It is also desirable to design the alkylation system so as to produce an alkylate which has a high octane rating.
Alkylation reaction apparatus known as open-pipe riser reactors comprise a vessel in which feed hydrocarbons are emulsified with liquid catalyst. The intimate contact between acid catalyst and hydrocarbons necessary for efficient reaction between olefin and paraffin is provided by injecting the hydrocarbons into the reactor through high-pressure nozzles in the form of a fine dispersion. Commercial open-pipe riser reactors are generally 20 to 40 feet in height and 2 to 4 feet in diameter. It is desirable in terms of economy and maintenance to reduce the size of commercial reactors and to minimize the flow of acid catalyst while maintaining the quality of the alkylate produced.
It is thus an object of this invention to provide an alkylation process and apparatus in which a high-octane alkylate is produced and acid circulation is minimized.
It is a further object of one aspect of the invention to provide relatively small alkylation apparatus.